Scope, limitations and outlook for HR-MS

The work presented in the previous sections demonstrates clearly that HR-MS provides much more information for the determination of the molecular formula when compared with LR-MS data. Exact masses alone already assist in the limitation of candidate molecular formulas, but the combination with MS/MS data (where available) clearly adds a significant improvement in eliminating false candidate formulas fiom consideration, for example through the use of combined match value. 

Current progress in this field is very rapid and improvements to the basis introduced here could include 

The measurements here were performed using pure standards, and measurements fiom real samples are likely to result in many more interferences in molecular formula 

The methods presented here can already be used to determine the molecular formula of unknown compounds from MS/MS data. A number of alternative strategies are also capable of this task (as mentioned above), including SIRIUS [243], MEF [256], MZmine [233]. Although the latter reference also includes a comparison with SIRIUS, no other comparisons between the approaches are available and, similar to MOL-GEN-MS/MS, most algorithms are only tested on a small data set due to the relative scarcity of high quality, publicly available MS/MS data. A systematic comparison of different approaches and different scoring functions would help to determine areas of future research. 

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